1. Field of the Invention
The invention relates to a magnetic head grinding method and an apparatus for grinding an object that has a plurality of magnetic heads arrayed thereon.
2. Description of Related Art
In a conventional batch type process for manufacturing thin film magnetic heads for use in disk drive devices of computers, an object to be ground has many converting portions including magnetic thin film arranged in a single array on a ceramic bar that will become sliders while cut into pieces, so that the throat heights of the gaps of the converting portions can be set to values optimized for reading and writing data signals.
In the case where the throat heights of magnetic heads are set to appropriate values during the grinding process, there is a problem that a ceramic bar, which is an object to be ground, is distorted and has therefore undesirable bends. That is, if the ceramic bar has distortions and bends, the ceramic bar cannot be ground uniformly by the grinding disk of the grinding apparatus. Therefore, there is a likelihood that the throat heights of thin film magnetic heads on both end portions of the ceramic bar will be so large or so small that the magnetic heads on both end portions become defective even though the throat heights of, e.g., thin film magnetic heads in the middle of the ceramic bar are proper.
To overcome this problem, a magnetic head grinding apparatus disclosed in U.S. Pat. No. 5,620,356 is designed so that a ceramic bar is ground by correcting bends thereof while measuring resistances that are varied in accordance with the throat heights of a plurality of thin film magnetic heads arrayed on the ceramic bar. As a result, the throat heights of the respective thin film magnetic heads formed on the ceramic bar can be set to proper values.
By the way, the conventional grinding apparatus such as proposed by U.S. Pat. No. 5,620,356 is constructed so that an object to be ground having many converting portions including magnetic thin film arranged in a single array on a ceramic bar is attached to the bottom surface of a platelike, horizontally elongated jig and that such horizontally elongated jig is further mounted onto a back plate disposed on the apparatus side. However, such conventional grinding apparatus imposes a problem that the attitude of the back plate having the horizontally elongated jig mounted thereon is not set with the grinding surface of the grinding disk as a reference. For example, in the case where the back plate is initially set vertical assuming that the grinding surface of the grinding disk is horizontal, the fact that the grinding surface is out of horizontality affects the accuracy with which to grind the object (the flatness of the grinding surface is reduced, and variations in throat height are increased, etc.).